According to a caregiver who spoke to the website, Wallace had been sick in recent months, although specific details are not known.

She had previously been diagnosed with breast cancer in 1985 and became a major public activist for beating the disease.

Wallace joined the cast of The Simpsons in 1990 and voiced Bart's fourth-grade teacher Mrs Krabappel, as well as other one-off characters such as Ms Mellon, a tutor at the Enriched Learning Center for Gifted Children which Bart transfers to in first season episode 'Bart the Genius'.

She won an Emmy for outstanding voiceover performance for her work on The Simpsons in 1992. According to IMDB, the actress appeared in 179 of the 551 episodes recorded to date.

Yeardley Smith, who plays Lisa Simpson in the series, paid tribute to her co-star on Twitter, writing: "Cheers to the hilarious, kind, fab Marcia Wallace, who has taken her leave of us. Heaven is now a much funnier place b/c of you, Marcia. Xx."

"I was tremendously saddened to learn this morning of the passing of the brilliant and gracious Marcia Wallace," added Simpsons executive producer Al Jean.

"She was beloved by all at The Simpsons, and we intend to retire her irreplaceable character."

Before joining the cast of The Simpsons, Wallace made her name as receptionist Carol Kester on The Bob Newhart Show and appeared on The Merv Griffin Show, ALF, Full House, Bewitched and Murder, She Wrote.

Wallace also appeared on stage in The Vagina Monologues and published a memoir titled Don't Look Back, We're Not Going That Way!.

The actress was due to turn 71 on November 1. Married to hotelier Dennis Hawley from 1986 until his death in 1992, she is survived by a son, Michael Hawley.